Egypt’s election commission on Tuesday upheld a ban on the country’s three leading presidential candidates - a former spy chief, a Muslim Brotherhood stalwart and a right-wing cleric - in a decision that immediately triggered demonstrations by some furious supporters.

Egypt’s election commission on Tuesday upheld a ban on the country’s three leading presidential candidates - a former spy chief, a Muslim Brotherhood stalwart and a right-wing cleric - in a decision that immediately triggered demonstrations by some furious supporters.

Each of the campaigns confirmed the decision after being notified by election officials; the commission had yet to issue a formal announcement by late Tuesday night.

The dramatic winnowing of the presidential race has stunned Egyptians, deepened concern over security at the polls next month, and fueled nonstop jokes and cartoons. A headline that appeared in The Economist magazine summed up Egypt’s candidate crisis: “And then there were none.”

Omar Suleiman, who served for 18 years as Hosni Mubarak’s spy chief and worked closely with the CIA, was disqualified because of problems with his required endorsement signatures. Muslim Brotherhood financier Khairat el Shater was snagged by a Mubarak-era conviction that strips him of political rights even though he’s been pardoned.

And ultraconservative Islamist Hazem Salah Abu Ismail was cut because his mother was found to be a naturalized U.S. citizen, in violation of a law that says a candidate must have two Egyptian parents. Abu Ismail claims that official documents proving his mother’s American citizenship are forgeries provided by officials in Washington in collusion with the ruling generals in Cairo.

The sudden departures of the three front-runners come just six weeks before voting begins, the latest snarl in a historic race that’s been entangled in controversies and conspiracy theories from the outset. With anger over the ruling, many Egyptians worry, the campaign season will get rougher still.

“The ouster of Shater, Abu Ismail and Suleiman is drawing a new map for the presidential elections. They owned the voters in all three fields they represent,” said Gamal Sultan, a Cairo-based researcher of Islamist movements and editor of the independent newspaper The Egyptians.

The remaining candidates _ among them former Arab League chief Amr Moussa and the pro-reform Islamist Abdel Moneim Aboul Fotouh _ had been viewed as weak and all but finished until the commission’s ruling. By contrast, the three disqualified candidates together represented constituencies that are millions strong. Some Islamist supporters already have begun a civil disobedience campaign as a show of force.

“Eliminating me from presidential elections despite my proper legal standing is evidence that Mubarak’s regime continues to rule. We will continue our peaceful struggle until the revolution is complete,” Shater, the Muslim Brotherhood candidate, vowed in a message that appeared on his Facebook and Twitter accounts.

Abu Ismail’s supporters, distinctive with their long beards and cropped gowns, massed in front of the election commission headquarters, briefly skirmishing with security forces guarding the building. Men in the crowd also attacked a TV cameraman who was broadcasting the scene live to a regional audience. Other Abu Ismail campaigners stopped the scuffle, witnesses said.

The violence erupted right after Abu Ismail made a surprise appearance at the demonstration. While his official Facebook page urges restraint among his followers, he was much more fiery in person, rallying his supporters to continue their sit-in at the commission office.

“Whoever believes in God and his prophet should not leave his spot!” Abu Ismail told the crowd. Supporters responded with chants of “God is great!”

Suleiman’s campaign, meanwhile, issued no statements on the ruling, promising to weigh in on Wednesday.

“The campaign is suspended after the news. We have nothing to say,” said Mohamed el Eshiri, a senior campaign worker.

Suleiman’s exit gives a boost to the once-flagging bid of Moussa, the longtime Arab League chief who’s anathema to revolutionaries because of his close ties to the former regime. However, the familiar Moussa could do well as the “safe” choice for some liberals, Coptic Christians, former-regime fans and other voters who are alarmed at the Brotherhood’s takeover of Egyptian political life.

The Brotherhood’s Freedom and Justice Party won nearly half the seats in Parliament, assumed control of Egypt’s biggest labor syndicates and dominated the now-suspended panel charged with drafting a new constitution.

Although the Brotherhood remains by far the largest and best-organized single bloc, many voters said they were withdrawing their support after the group reneged on a promise not to field a presidential candidate. In fact, the group fielded two candidates _ the now-barred Shater and a backup, party leader Mohamed Mursi, whose name presumably will replace Shater’s on the ballot.

Even with a spare contender, however, the Brotherhood quickly added its weight behind the criticisms of the election panel’s decision.

“The committee began rigging the elections today,” the Muslim Brotherhood’s top attorney, Abdelmenem Abdelmaksoud, told the Al Jazeera satellite TV channel in an interview after the ruling.

“The committee is choosing what best serves its interests,” he added, “and this is an obvious and bold forging of the upcoming elections before they even start.”